Method and apparatus for separating materials.



WIA'HESSE 7 f% D. W. TROY. METHOD AND APPARATUS FOR SEPARATINGMATERIALS. APPLICATION FILED APR. 24, 1911.

1,024, 1 0 9. Patented Apr. 23, 1912.

ImIEn mT COLUMBIA PLANOGRAPH COHWAVSHINGTON, D. c.

DANIEL W. TROY, OF MONTGOMERY, ALABAMA.

METHOD AND APPARATUS FOR SEPARATING MATERIALS.

Specification of Letters Patent.

Application filed April 24, 1911.

Patented Apr. 23, 1912. Serial No. 622,932.

To all whom it may concern:

Be it known that I, DANIEL W. TROY, a citizen of the United States, anda resident of the city and county of Montgomery, State of Alabama, haveinvented certain neWand useful Improvements in Methods and Apparatus forSeparating Materials, of which this is a specification, reference beinghad to the accompanying drawing, forming part hereof.

The invention relates to the separation of materials with respect totheir electrical conductivity and its object is to provide new anduseful methods and means for employing this characteristic of materialsto efliciently and economically disassociate the elements of mechanicalmixtures, such as of ore and matrix, etc., as will be more fully pointedout hereinafter.

In the drawing, which is a diagrammatic illustration of the apparatusemployed, except such types of crushers as may be used to grind thematerial to the required fineness and which form no part of theapparatus of the invention, Figure 1 shows a side elevation and partlysectional view of the separator; Fig. 2 is a diagram illustrating theelectromagnetic elements; Fig. 3 is a sectional View (on a larger scale)of the magnet cores; and Fig. 4 shows a possible modification of coreand core-winding.

The method consists broadly in causing mixed materials such as graphiteand silica, in a more or less finely divided or granular condition, tobe subjected to the action of a magnetic flux moving relative to theparticles of material at what is in fact an enormous rate of speed. Anessential of the invention is that the speed of the flux relative to theparticles be as high as possible (or rather near the limitations whichthe hysteretic constants of the iron employed will permit). This will bereadily understood from the description to follow. Assuming the mixedparticles, say silica and graphite, to be freely falling through space,if they are engaged, for want of a better term, by this swiftly movingflux, Foucault or eddy currents will be set up in the graphite particlesto an extent much greater than in the less conducting particles ofsilica. A moments reflection, however, will satisfy an electricalengineer that the speed of relative motion of the flux, at least withsuch flux densities as known magnetic cirtion of any particle cuitspermit, must be extremely high. The reason being that to induce one voltE. M. F. in the circuit formed by the peripheral por- 100,000,000 linesof force must be introduced (or removed) per second. WVith particles ofsubstantial ize, such as base-balls of copper and base-balls of mica,the area of cross section of which would include several square inches,a moderate speed could be employed to effect a substantialdifferentiation, but where the particles have a diameter something likea fraction of a millimeter or even smaller, it is at once obvious thatthe flux must move with a tremendous velocity to effect substantial E.M. F. tending to develop an eddy current in the particle.

In the drawing, Fig. 1 shows a combina' tion of apparatus for effectingthe separation in a practical manner.

1 is a pipe or discharge member for feeding the mixed granular materialto the apex of a cone or spreader 2. The cone shape is a convenient andpreferred form. At the base of the cone the particles, separated by thedescent into a thin conical layer, drop in a more or less paraboliccurve through an annular opening, also inclined more or less parallelwith the slant of the cone, whence they are free to fall either in orout of a receiving bin 8. The annular opening 3 is the space between twoconcentric rings of iron or other magnetic material, see 4 and 5, of thefigure, one of which forms the magnet and the other the armature of theelectromagnetic system. Windings are repre sented by 6, 6, Fig. 1. Bothrings are shown partly broken away and in section so as to clearlyindicate their relative positions and the annular opening through whichthe mixed particles fall after leaving the spreading cone 2. In thediagram, Fig. 2 the outer ring is indicated at 4, the inner at 5 (therings in this case being shown without slant and merely to illustratethe electromagnetic details) 6, 6, 6, are three windings star-connectedto a three-phase alternating circuit, as from the three-phase alternator7 I do not confine myself to the use of two, three, or any polyphasecurrent; the function of the out-of-phase windings is merely to producea rotating field, which in the structure illustrated will set up twoopposite fluxes between the inner and outer rings, opposite,

however, only in position, as they will, of course, simply be the twoair-gap portions of the same flux. By employing alternating currents ofgreat frequency it is quite possible, especially with the dimensions ofrings which will be adopted in practice, to produce a velocity ofrotation of these two air-gap fluxes which, compared with meremechanical rotational speeds may be aptly termed enormous. Taking thecircumference, mean, as feet, and the current as one of say 500 cycles,(although very much greater rate of alternation may be employedexistingdynamos being perfectly adaptable for this purpose) it is evident thatthe flux-brushes, as we may term the two air gap portions of the flux,will rotate at a speed of 15,000 feet per second, and, as there are twoof these air-gap fluxes, it follows that if a particle takes half asecond to drop through the space between the rings it will be struck bya flux-brush many times before it can drop through. The limitation onthe speed of travel of the fluxbrushes is obviously to be determined bythe hysteretic constants of the iron employed I as there is no troublein obtaining enormous speeds of alternation (see the special generatorsemployed in wireless work.) Assuming the eddy currents thus generated inthe particles it is at once evident that those particles having thegreatest eddy currents will be dragged tangentially by the rotating fluxand will take, in addition to their rate and direction due to gravityand the slant of the cone, an additional rate and direction due to thistangential drag, the eifect being to cause these particles to fallbeyond those not so dragged; in other words the particles acted uponwill leave the cone (or rather the prolongation of the cone through theannular space 3) in much the same manner as if, while they had beenfalling or sliding down the cone, the cone had been whirling on its axisof figure. The nonconducting partlcles, however, not having the Foucaultor eddy currents generated in them to any great extent, will not beacted on or dragged by the flux and will fall substantially as if therewas no flux present.

At 11 and 12 I have attempted to illustrate the paths 'of thenon-conducting and conducting particles respectively. At 8 is shown areceiver or bin adapted to catch the tailings, the concentrates beingreceived on the floor 10 (which may be that of a suitable bin or otherreceiver). As the path of the tailings is apt to vary with differentconditions of atmospheric moisture, moisture of the mixture, and otherelements, I preferably provide means for varying the height of the mouthof the bin 8 (see the slotted member and clamping nut 9). Obviously amere up and down adjustment of the bin 8 will suffice to cause it toform the base of the paraboloid of revolution or whatever the figure maybe the surface of which is represented by the falling tailings.

It will be usually necessary to laminate the rings more or less inplanes normal to' rotating field motors may be employed with certainadvantages. Such a structur is indicated at Fig. 1, the laminated ring(only part of which is shown) being cut with winding slots as at 13,through which suit able windings (one shown at 14) may be threaded. Itis needless to point out to those skilled in the art of constructingalternating current induction motors the manners in which a rotatingmagnetic field may be produced Without the rotation of any mechanicalparts. This separator is, in fact, what may be termed a squirrel-cagemotor, the conducting particles forming the conductors in which currentsare first induced and by which the conductors are dragged by the field.In principle it is precisely a squirrel cage or induction motor, but, aspointed out before, owing to the minute size of the conducting membersthe speed of rotation of the fiuxmust be tremendous compared with anypossible rates of mere mechanical rotation. This high rate of relativespeed between conducting particles and flux has besides the essentialcharacteristic noted an additional advantage, that is to say, the highspeed of rotation directly increases the tangential drag on theconducting particles carrying eddy currents and by the very fact of thehigh speed of flux rotation a particle carrying, as all will, a minutecurrent, will be dragged tangentially with a considerable forcethecondition of successful operation with the particles which will beemployed.

Little more need be said about the method as it is fully evident fromthe foregoing. In treating ores having greater conductivity than thematrix the ore and matrix is first crushed or ground, the machineryemployed being that most convenient. The degree of fineness of themixture will be determined by conditions of the particular ore-ingeneral it must be sufiicient to insure mechanical separation of grainsof ore from grains of matrix or rockin other words the system isunreliable where ore and rock are agglutinated or form a single compoundgrain or particle. The pulverized or granular mixture is fed by gravityor otherwise through the air gap and while passing through is operatedupon by the swiftly moving flux. In operating upon gold bearing sands toextract the gold from the sands,

or in other cases Where the material is naturally in a granular orpulverent condition, the first stepthe grindingis of course needless. Inother cases it forms an essential of the method.

As an alternative of the precise steps indicated the concentrates may bemade to lag and the tailings be allowed to take the direction whichgravity and the slant of the spreader may give them if the rings beformed as shown in Fig. 1 and Wound With a single Winding or itsequivalents and the current simply alternated so as to reverse the fluxclirectionsthrough the falling particles Without a movement of rotationof any sort. In this case it will generally be found necessary toalternate the flux at a high rate of speed and to increase the distanceWhich the particles must fall through the rapidly reversing flux.

From the foregoing it will be seen that the essential element of thisinvention is the use of a flux speed of sufiicient rate to produce notonly an effective induction of eddy currents in the relatively minutepar-" ticles which Will be met With in practice but which will producean appreciable drag upon these particles after such currents areinduced; both of these factors making for a complete separation of theore from the tailings. In the modification last described the essentialis still an excessively high rate of reversal of magnetic field, but thefunction of the field is merely to produce the eddy currents and then byreason of its density to act as a drag or brake to check the downwardvelocity of the particle.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents.

Having described my invention, What I claim is:

1. In apparatus of the class described, concentric rings of magneticmaterial forming parts of a magnetic circuit and separated by aninclined air-gap, means for feeding particles of nonmagnetic material ina trajectory through said inclined airgap, and a vertically adjustablereceptacle beneath said air-gap adjustably adapted to intersect saidtrajectory, substantially as set forth.

2. The method described, consisting in feeding a mixture of non-magneticparticles of different electrical conductivities in a plurality ofmutually divergent and substantially parabolic trajectories through thelocus of a magnetic field, varying said field in said locus and settingup eddy currents in said particles to vary the trajectories of thedifferently aifected particles.

3. The method described, consisting in feeding a mixture of non-magneticparticles of diiferent electrical conductivities in a plurality ofstubstantially parabolic trajectories through the locus of a magneticfield, varying said field in said locus and setting up eddy currents insaid particles to vary the trajectories of the difl'erently affectedparticles.

Vi itness my hand this 18th day of April, 1911.

DANIEL WV. TROY.

In the presence of DAISY J ONES, THOMAS J. Scorr.

Washington, D. C.

